The removal of contaminants from the surface of textile articles and textile processing equipment is a significant concern within the textile industry. The presence of surface contaminants is particularly troublesome within dyeing operations, especially within fabric dyeing processes. A wide range of surface contaminants may potentially be present within a given fabric dye cycle, including residual dyestuffs from either the present and/or previous dye cycles and/or oligomers.
Processes and compositions have been developed that attempt to reduce the amount of textile contaminants present during dyeing. For example, dye machine cleaning procedures, referred to in the art as “boil-outs,” have evolved over time to reduce the build up of textile contaminants on the surfaces of dye machines. Boil-outs generally involve recirculating a cleaning composition through an otherwise empty dye machine. Boil-outs are typically conducted at an elevated temperature, for example a temperature of about 270° F., for an extended period of time, such as about 3 to 6 hours. Conventional boil-out procedures thus incur expense due to both the increased utility costs associated with heating the dye bath and the extended downtime involved.
Conventional boil-out compositions are typically highly alkaline, with exemplary compositions exhibiting pHs of up to 12. An exemplary conventional boil-out composition may include about 9 to about 10 weight percent caustic, about 2 to about 5 weight percent reducing chemical, and about 5 to about 20 weight percent solvents, based on the weight of the boil-out composition. Conventional boil-out compositions thus present possible environmental concerns due to their high alkalinity and use of solvents.
Boil-out procedures are generally designed to remove residual dyestuffs from the walls of the dye machine, and may be used with all types of textile dyes and dyeing equipment. It is important to remove any residual dyestuffs remaining after a dye cycle because it may adversely affect the shade and/or levelness of subsequent dyeings within the dye machine. The removal of residual dyestuffs from a dye machine is of particular importance when changing from the dyeing of dark shades to light shades within a dye machine. However, in addition to reducing the amount of residual dyestuffs, boil-out processes may also be intended to remove other contaminants, depending on the type of fabric being dyed. For example, boil-out procedures performed in conjunction with the dyeing of polyester fabrics are generally intended to remove both oligomeric deposits and residual dyestuffs from the surfaces of the dye machine.
Polyester fibers inherently contain oligomers, or small molecule polymers, as a by-product. Trimer is the predominate oligomeric species within polyester fiber formed from polyethylene terephthalate. Trimer tends to bloom to the surface of the polyester fiber as it is being processed at elevated temperatures. Thus trimer generally rises to the surface of polyester fibers during dyeing, particularly under the high temperature conditions commonly utilized during the disperse dyeing of polyester fibers. In addition to migrating to the surface of the polyester fiber, a significant portion of the migrating trimer also typically enters the dye bath during dyeing.
Trimer within the dye bath is particularly problematic because it forms deposits on the surface of the fabric or yarn being dyed, as well as on the walls of the dye machine. Such trimer deposits on fabric or yarn surfaces do not dye evenly and remain as visible crystals after dyeing, yielding off quality goods. Trimer deposits on the polyester fiber also increases the frictional resistance of the resulting fabrics or yarns, ultimately leading to filament breaks during textile processing. Trimer deposits on polyester fabric or yarn also form a powder or dust on guide devices as the fabric or yarns travel over the devices, further exacerbating frictional resistance and quality issues. Trimer deposits on the walls of the dye machine can negatively impact the quality of dyed goods processed within the machine because such deposits may precipitate upon the surface of the dyed goods as they are being cooled at the end of the dye cycle. Thus trimer deposits lead to millions of dollars annually in waste and rework.
Processes and compositions have been developed that attempt to address the trimer issues associated with polyester goods. For example, alkaline solutions used to reduce trimer are discussed in U.S. Pat. No. 4,294,576. However, such alkaline solutions are not generally effective in removing trimer. Similarly, aromatic carboxylic acids in conjunction with halogenated hydrocarbons, polyethylene/polypropylene oxide block copolymer, and alkylene oxide adducts are known for treating polyester fiber, as described in U.S. Pat. No. 4,155,856. Phthalic ester compositions have also been developed to treat the polyester fabric, either during or after dyeing, as discussed in U.S. Pat. No. 4,229,176. However, such phthalic ester compositions adversely affect soilability, especially in reference to dry dirt.
Thus there remains in the art a need for compositions that are capable of effectively removing trimer from the surface of polyester fiber without significant detriment to the remaining fiber properties. There is also a need in the art for a composition capable of holding trimer in suspension in the dye bath until it can be flushed from the machine, rather than forming unwanted deposits. There further remains a need in the art for a composition and process for use in removing trimer and other textile contaminants from the walls of dyeing equipment which may employed at comparatively low temperatures for a comparatively short amount of time.